   []
   {:title \"REQUIRED\"
    :subtitle \"\"
+   :header-image \"\"
    :excerpt \"\"
    :author \"REQUIRED\"
    :twitter \"\"

(def stub-metadata
"{:title \"REQUIRED\"
 :subtitle \"\"
 :excerpt \"\"
 :author \"REQUIRED\"
 :twitter \"\"

(def rfc5322-content
"Subject: REQUIRED (title)
Subtitle:
Header-Image:
Excerpt:
From: REQUIRED (author)
Twitter:
